I've updated the Mt. Rainier NP photo guide news and information, the conditions and access, and the August prospects Web pages for corrections from the late July information. There wasn't much new, just a small updates.
The NP is almost snow free below 6,000 feet, and snow only persists 5-6,000 feet on north facing slopes, in shaded areas and on some sections of the Wonderland Trail (latest NP information). All the facilities are open and busy. All trails are good except some in the extreme backcountry areas where they haven't been repaired yet from the winter's snowpack and spring snowmelt.
Outside of that, it's just a good time to be there. Early August is good for the higher elevations meadow and alpine areas. But expect lots of bugs as it's the peak season for them until the first freezing nights, after which hiking and camping is excellent during the good weather days. And this usually last into early-mid September, later with Indian summers.
For photo opportunities, there's everything you want, and nothing to stop you except researvations at campground and backcounty camp sites. You can check the NP Website for researvations or hope to get there early for the daily openings. Otherwise, enjoy and photograph to your heart's content.